Our present invention relates to a cross-roll straightener and, more particularly, a straightener for bar stock, blanks and the like in which a lower roll and an upper roll have their axes crossing and the angle formed by these axes about a vertical axis is adjustable.
German patent document DE-AS 19 10 879 discloses a cross-roll or inclined-roll straightener which is comprised of a lower yoke, an upper yoke and columns connecting these yokes into a mill frame. The upper and lower rolls are journaled in roll frames on the lower and upper yokes and the roll frame on the upper yoke can be adjusted relative to the roll frame and the lower yoke by an adjusting spindle in the vertical direction. Means is provided, in addition, for adjusting the cross angle of the roll axes about the vertical central axis of the straightener.
In this patent document, the lower yoke is provided with a vertically-movable slider which is actuated by a piston and cylinder unit. For the straightening of so-called blank stock (drawn, peeled or bright rounds or bar stock) the roll frame carrying the lower roller is braced directly on the lower beam or yoke of the frame. For the straightening of so-called black stock (unworked bars with incompletely round cross sections), the piston and cylinder unit is actuated with an adjustable pressure to lift the slider carrying the lower roller from its abutment with the lower yoke or beam and a yieldable bracing of the lower roll takes over. During the introduction and discharge of a bar to be straightened, the roll or straightening gap can be opened by pressure relief of the piston-cylinder unit. The yieldable bracing provides protection against overloading.
In the inclined-roll straightening technique, reaction forces of varying magnitude act upon the rollers which produce transverse forces and torques upon the roller frames about the vertical axis. These forces and torques must be taken up directly by the lower yoke for the lower roller and by the upper yoke and the columns of the press frame for the upper roll. When the upper roll in such a straightening machine is advantageously mounted in a bed received between the yokes and guided in the press frame, these considerations apply between the bed and the columns depending upon the play. Countering these phenomena may be a readjustment of the bracing of the upper roll for the straightening of black stock as a consequence of the nonround character thereof and the diameter differences.
It is, therefore, an object of the invention to provide an improved inclined-roll or cross-roll straightening machine of the aforedescribed type so that both blank stock and black stock be effectively straightened without drawbacks of the type which now characterized such machines.
Another object of the invention is to provide an improved cross-roll or inclined-roll straightening whereby problems which have hitherto been encountered in utilizing the columns of the machine for guidance purpose can be obviated.
These objects are attained, in accordance with the invention in a cross-roll straightening which comprises:
a frame comprising a lower yoke, an upper yoke, and four vertical columns at corners of a rectangle connected between the yokes;
a lower roll mounted on the lower yoke;
a roll bed vertically shiftable on the upper yoke;
an upper roll mounted on the roll bed and cooperating with the lower roll and having a roll axis crossing a roll axis of the lower roll for straightening stock passed through a gap between the rolls in a feed direction, the roll axes being at an angle to one another about a vertical axis;
a spindle and nut device between the roll bed and the upper yoke for vertically positioning the upper roll relative to the lower roll;
a respective vertical guide track formed on each of the columns and respective guide surfaces on the roll bed riding on each vertical guide track;
a respective adjusting device between each column and the respective guide track, the adjusting devices including a pair of upstream adjusting devices and a pair of downstream adjusting devices with respect to the direction, one of the adjusting devices of each pair being a hydraulic adjusting device with a respective double-acting adjusting hydraulic cylinder and the other adjusting device of each pair being a mechanical adjusting device, the adjusting devices rotating the bed about the vertical axis to vary the angle; and
a further double-acting hydraulic cylinder on the upper yoke for applying axial stress to and relieving axial stress on the spindle and nut device.
More particularly, the upper roll is mounted on a roll bed constituting a member received between the upper and lower yokes within the frame formed by these yokes and the columns and has four guide surfaces which slide along guide tracks on the column which can be adjusted by positioning wedges, shimming bars and like adjusting devices and these adjusting devices are provided in pairs. One pair of adjusting devices is relatively upstream and the other pair is relatively downstream with respect to the direction of displacement of the stock through the apparatus and between the rolls.
According to the invention, one of the adjusting devices of each pair has its adjusting wedge hydraulically displaceable by a double-acting piston-cylinder unit whereas the other adjusting wedge of that pair is mechanically adjustable. The roll bed is connected to the yoke in that it has a hollow pin for a guidance in the upper yoke and formed with a threaded nut engageable by a threaded spindle on the yoke. This adjustment spindle, in turn, is braced axially by a double-acting piston and cylinder unit which, when it generates forces, prevents the spindle from rotating in the nut.
These features ensure that with a simple hydraulic cylinder control, a prestressing of the straightening machine can be effected with a clamping of the guide plane, especially for the straightening of blank material, so that the rolls and their supports are braced rigidly with respect to one another. It also allows a floating support for the upper roll with adjustable straightening pressure or play for the straightening of black stock. A double-acting piston and cylinder unit for the spindle and nut between the roll bed and the upper yoke serves to take up any play in the mutually-engaging threads of the spindle and yoke.
According to a preferred feature of the invention, the stressing piston and cylinder unit acting on the spindle and the piston and cylinder unit for hydraulically displacing adjusting wedges are simultaneously supplied with maximum pressure. In this state, the straightening machine is rendered free from any play and is under maximum prestress so that the straightening machine can operate with the straightening gap height determined by the spindle. With simultaneous shifting of the positioning wedges, any play in the displacement of the roll bed can be reduced to zero and blank stock can be reliably straightened.
The clamping piston and cylinder unit of the adjusting spindle can have maximum pressure applied thereto while the piston and cylinder unit of the hydraulically actuated wedges can be pressureless. This allows straightening of blank stock without active clamping of the lower plane, i.e. with a minimum adjustable play.
The invention affords however an alternative operation in that with a straightening gap which is smaller than the diameter of the stock to be straightened, the stressing piston and cylinder unit can allow a floating of the spindle while the piston and cylinder units of the hydraulic wedges are relieved of pressure. This provides the conditions necessary for the straightening of black stock whereby the straightening gap is smaller by an amount, say, of x than the actual diameter of the straightened stock.
The stressing piston and cylinder unit then permits a floating of the bed by a magnitude x and compensates for the deviation between the gap width and the diameter of the stock to be straightened. Since, in this case, the lower guide plane, i.e. the roll bed, can be displaced without active clamping by the adjustment wedges, the roll bed can make up for the difference x. The play permitted the roll bed can be adjusted by the adjustment screws of the mechanically-shiftable wedges.
A pressure-limiting valve can be provided on the pressure side of the system supplying the stressing piston and cylinder unit such that a fallback counter to the straightening force is possible.
According to a feature of the invention, on the upper yoke a further piston and cylinder unit can be provided to act upon the roll bed via a tension bar.